In electrically driven vehicles such as hybrid vehicles or electric vehicles, a step-up/down convertor (power conversion apparatus) is used in which a voltage of a battery is stepped up to supply the stepped-up voltage to a motor generator while a voltage of electrical power generated in the motor generator is stepped down to charge the battery with the stepped-down electrical power.
In recent years, power conversion apparatuses have come into use, in which a combination of two batteries and four switching elements is incorporated to step up and down the two batteries connected in series or to step up and down the batteries connected in parallel (refer to, for example, JP 2012-70514 A).